1. Field of the Invention
The invention relates to an artificial airway device, more specifically to a supraglottic airway designed to have increased internal pressure during introduction of artificial positive-pressure ventilation.
2. Description of the Related Art
In general, supraglottic airways such as laryngeal masks allowing for both rapid lung ventilation and the insertion of medical instruments and tubes into the laryngeal openings of patients have been described in patents, such as U.S. Pat. No. 4,509,514 to Brain and U.S. Pat. Nos. 6,422,239 and 5,937,860 to Cook the entire disclosures of which were herein incorporated by reference. Laryngeal masks generally consist of two major components, a breathing tube and an inflatable or rigid shield, these devices are inserted into a patient's throat, and when properly positioned, cover the laryngeal opening. A seal is then formed around the circumference of the laryngeal opening by the inflation of a ring-like structure located toward the front of the mask (patient end). Inflation of the ring exerts pressure against the front, sides, and rear portions of the oropharynx, securing the device in place such that the laryngeal opening is positioned in alignment with a recessed cavity in the mask face. Alternatively, the structure of the shield may be formed as a large semi-rigid plastic construct which generally serves to seal by contouring to the shape of the throat and imparting pressure on the throat by its own size and shape effectively filing available space.
Extending from a point external to the oral cavity, the flexible breathing tube terminates within the recessed cavity, aligned axially with the laryngeal opening. The positioning of the flexible breathing tube allows the passage of endo-tracheal tubes or related medical instruments into the laryngeal opening, in addition to allowing for positive-pressure lung ventilation.
While current supraglottic airways such as laryngeal masks can provide for improved placement and breathing over a traditional endotracheal tube, they can be improved. In particular, the use of inflated structures or semi-rigid plastic constructs to hold the device in place in the throat can lead to undesirable pressure on throat tissue. Current designs seal the laryngeal opening inside the recess by exerting a constant pressure on surrounding tissue effectively forcing the structure of the mask into the walls of the throat while it is in place. This constant pressure is generally not relieved until the device is removed. While the structure of these devices are generally made pliable and soft so as to minimize potential damage from their near constant contact with throat tissues, the constant pressure they impart on potentially sensitive structures in the throat can, in some cases, lead to tissue fatigue and damage.
The problem is exacerbated by the fact that the person inserting the airway generally has little to no control on the pressure exerted by the airway and often has no indication thereof. Thus, the device can easily be accidentally over-inflated or over-sized exerting more pressure than is necessary or desirable on the tissue of the throat, often without realizing it.